Guided frangible slips



Feb. 24, 1970 w. o. R A 3,497,002

GUIDED FRANGIB LE SLIPS Filed July 11, 1968 2 Sheets-Sheet 1 W/ ///am 0.Be r/ yman INVENTOR.

RYMAN Feb.- 24, 1970 Filed July 11, 1968 W////am 0, .15 e r/j/mz/r YINVENTOR.

United States Patent M 3,497,002 GUIDED FRANGIBLE SLIPS William 0.Berryman, Houston, Tex., assignor to Schlumberger TechnologyCorporation, New York, N.Y., a corporation of Texas Filed July 11, 1968,Ser. No. 744,171 Int. Cl. E21b 23/06, 33/ 1 28, 33/129 US. Cl. 166123Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Thisinvention relates to a well tool and more particularly to anchoringmeans on a well tool.

Packers or plugs which are permanently set in a well bore typically useslip type anchoring means. The slips are generally provided with teethor wickers on their external surface which, when the slips are expanded,bite or dig into the casing or tubing wall to couple or anchor the welltool in the well bore. If it is later desired to remove the tool, thiscan be accomplished by drilling, milling or chipping. In these cases itis desirable to fabricate the slips, as well as the tool, from afrangible material such as cast iron so that it may easily be broken upby the action of a drill bit.

The slip assembly normally must be maintained in a retracted positiondring passage through the well bore until such time as it is desired toanchor the tool by setting the slips. At this time, the tool is actuatedand the slips are forced radially outward to engage the surroundingcasing.

The slips must be readily movable in a radial manner when desired, butnot so easily movable that they can inadverently be actuated andexpanded during passage through the well bore. One prior art approachhas been to use shear screws or pins to releasably retain separate slipmembers relative to the tool body until a setting point is reached. Uponactivation of the tool, these pins are sheared to allow the slips to beextended into gripping contact with the casing.

Another approach taken in the prior art has been to use a one-pieceannular slip construction of a frangible material such as cast iron. Toset such slips, a conical or frusto-conical expander is forced insidethe slip member and fractures the frangible material to form slipsegments. To enhance and control this breaking action, the slipconstruction can have weakened sections aolng longitudinal lines.Obviously, such a one-piece slip construction eliminates the need forshear pins or screws to prevent accidental setting.

To insure the best possible anchor of the slips with the casing, thebroken slip sections should engage the casing in such a manner that theyare aligned in a horizontal plane (a plane at right angles to thelongitudinal axis of the casing) as well as being uniformlycircumferentially distributed about the circumference of the inside ofthe casing. If these two conditions are not both met, then the gripprovided by the slips will not be as uniform and 3,497,002 Patented Feb.24, 1970 powerful as is possible. The uniform circumferentialdistribution of the slip segments will assure that the well tool iscentrally aligned in the bore of the casing. If the slip segments arebunched on one side of the casing the tool body will tend to be pushedaway from the side of the casing which contains most of the slipsegments. Additionally, this will tend to weaken the grip of the bunchedsegments because the tool will be able to flex or move away from themand an even distribution of setting pressure will not be maintained.

Because there is no practical way to assure that the breaks along thelongitudinal weakened sections will all occur precisely at the sameinstant in time, means can be provided to promote horizontal alignmentof the broken slip sections. Otherwise, the first slip segment whichbecomes free to move can separate from the remaining, as yet unbroken,segments and slide down the expander cone and become wedged between theexpander cone and the wall of the casing. If this happens, the expandercone will cause the teeth of that segment to engage the casing first.This will prevent the free upward movement of the expander cone tofurther fracture the slip assembly and anchor the other segmentsthereof, as they are broken.

This problem is more troublesome in the case where the Well bore is notvertical but rather is inclined or slanted. Here the tool will generallybe oif center in the well bore when setting is started. In this case, ifone slip segment becomes separated from the others and slides down theexpander cone prematurely, it can wedge itself in the widest part of theannular space between the tool and the casing. If this occurs, it willkeep the tool oif centered in the well bore and the maximum efiiciencyof the packing element will not be realized.

This problem has been recognized in the prior art and various attemptsmade to obviate these difiiculties. In segmented slips, snugly fittingand loosely fitting horizontally aligned guide pins joining the slipsegments to maintain some mechanical linkage between the sections and,thereby, maintaining horizontal alignment of the sections duringexpansion have been used. Another approach has been to equip breakableslips with internal powerful expander springs to thrust and propel thebroken sections radially into immediate contact with the casing walls assoon as they are broken. Prior art attempts to achieve uniformcircumferential distribution of slips have relied on the use of weakenedsections of differing strengths programmed to break in a given sequencewhen acted on by the expander cone. Further, various radial guidingmeans have also been utilized such as guiding bars runninglongitudinally through the slips and guide pins radiating outwardly fromthe central tool body and carried in bores or slots in the slipsections.

The present invention does not use complicated spring arrangements,guide pins carried in bores, or weakened sections of different strengthsto maintain horizontal and circumferential alignment of the broken slipsections, but rather makes use of a more simple frictional bandarrangement in combination with a specially shaped setting tool in orderto accomplish this end.

Accordingly, it is an object of this invention to provide a well toolwith an anchoring means including a onepiece frangible slip and acombination of effective economical means for maintaining the horizontaland circumferential alignment of corresponding portions of slip segmentswhen broken.

SUMMARY OF THE INVENTION In the well tool of the present invention, theanchor means include a unitary, hollow, cylindrical slip member of afrangible material such as cast iron. The outer surface of this memberis provided with a plurality of circumferential teeth or wickers forengaging the well casing in a gripping manner upon fracture andexpansion of the slip member by an expanded cone. The lower portion ofthe inner surface of the annular slip member embodying the presentinvention is conically tapered over a portion of its length tocooperatively engage an expander cone which is slidably mounted on thewell tools central body. The remainder of the inner surface of theone-piece frangible slip member is of a uniform circular diameter suchas to provide a sliding fit with the central body of the well tool. Theupper shoulder of the slip member is provided with raised tang portionsto cooperatively engage corresponding notches on the lower end of asetting tool. The setting tool is releasably coupled to the upper end ofthe well tool.

The tangs on the upper shoulder of the slip member cooperativelyintermesh with the notches in the setting tools lower portion tocircumferentially guide broken portions of the slip assembly as theassembly is expanded radially outward by the expander cone. This assuresa symmetrical circumferential distribution of the broken portions of theslip assembly about the inner wall of the well casing.

A plurality of longitudinal weakened sections are defined in the slipmember by a plurality of external longitudinal notches cut at uniformintervals about the circumference of the member. These notches do notextend completely through the cylindrical wall of the member. Acircumferential, flanged, retaining groove is provided in the externalsurface of the slip member. This groove carries within it and retainsthere a unitary expansible steel band which, when the expander cone actson the slip to fracture it into separate sections, maintains thehorizontal alignment of corresponding portions of these broken sections.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation together with further objectsand advantages thereof, may best be understood by way of illustrationand an example of an embodiment when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic partiallysectioned view illustrating the present invention utilized as an upperslip on a wireline set tool in a well bore.

FIGURE 2 is a longitudinal elevation of the slips embodying the presentinvention showing the notch and tang arrangement on its upper shoulderand showing the oneway expansible steel band carried in a retaininggroove about the external surface.

FIGURE 2A is an enlargement showing in more detail the retaining grooveon the external surface used to retain the unitary one-way expansibleband.

FIGURE 3 is a top view of the same embodiment of the present inventionshowing in more detail the shape of the raised tang portion on its uppershoulder which cooperatively engages the corresponding setting toolnotches.

FIGURE 4 is a view in cross section of a portion of the setting toolshowing the notches in the lower end thereof which engage the raisedtangs on the upper shoulder of the present invention.

FIGURE 5 is a schematic view showing the action of the retaining notchand extension combination of the setting sleeve and upper slip shoulderwith the broken sections of the slip assembly nearly in fully expandedposition.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention concernsan improved unitary breakable slip for use on well tools by which theslip attains improved gripping with the walls of the well casing byutilizing a novel combination of means to assure proper horizontal andcircumferential alignment of corresponding portions of the broken slipsegments when set.

In FIGURE 1, a well casing 11 is shown traversing earth formations andcemented in place. A well tool 12, such as a permanent bridge plug, issuspended in casing 11 by means of a wireline 13. Wireline 13 is coupledto a setting tool 14 which is releasably coupled to bridge plug 12.

Bridge plug 12 has a central mandrel 15 which carries from top to bottoman upper slip assembly 16, an upper expander 17, a packing element 18, alower expander 19 and a lower slip 20. The arrangement is such that whenmandrel 15 is moved upwardly, expander cone 17 acts to fracture upperslip 16 and expand the broken segments thereof radially outward intosetting contact with the well casing 11. Further upward movement ofmandrel 15 causes expansion of packer element 18 and upward movement oflower slips 20 over lower expander 19 into setting engagement with thewall of the casing 11. A oneway body lock 21 connects mandrel 15 andupper expander 17 to one another to prevent the mandrel from movingdownwardly relative to expander 17 when the setting process is finished.At this point, setting tool 14 is released and withdrawn on wireline 13leaving plug 12 permanently anchored to the casing.

Lower slips 20 have alternate, longitudinally extending grooves fromrespective end surfaces to provide an integral annular member which canbe radially expanded without fracture of the member. Further details onlower slips 20 can be found by reference to U.S. Patent No. 3,298,440.

The upper slip assembly of bridge plug 12 is shown in detail in FIGURES2, 2A and 3. A one-piece frangible slip element 16, preferably made ofcast iron, is provided with teeth or wickers 16a on its external surfacefor grippingly engaging the wall of well casing 11. Longitudinalweakened sections are provided in slip member 16 by a plurality oflongitudinally extending notches 22 extending partially through itsthickness. The upper portion of the annular slip member 16 is providedwith notches 23 which form upwardly extending tangs 24 for cooperativelyengaging with downwardly extending extensions 31 and notches 33 in asteel setting sleeve 32. Setting tool notches 33 have parallel radialedges and are sized to a width slightly wider than tangs 24. Theclearance provided by this excess width is suflicient to allow slightrotation of broken segments of slip member 16 as the broken segments areexpanded radially outward and assume the larger circumference of thewell casing 11. It should be noted that tangs 24 appear in aconfiguration such that each of the tangs 24 extends over acircumferential portion of annular member 16 containing two of theweakening notches 22 and that thereby setting tool notches 33 eachengage portions of three sections of slip member 16 when broken.

A circumferentially extending recess 26a, of uniform diameter isprovided in member 16 near its upper shoulder and is adapted to receivetherein a unitary expansible steel band 25. Recess 26a, shown in largerdetail in FIG. 2A, has upper and lower annular grooves 27 formed byupper and lower flanges 26. At one point around the circumference ofmember 16 there is a circumferential gap 28 provided in both flanges 26.Gap 28 is sized so as to permit band 25 to be inserted into recess 26a.Band 25 is greater in length than the circumference of recess 26a andthe width of the grooves 27 is greater than the thickness of band 25 sothat the band can he slid around the circumference of recess 26a untilit completely encircles member 16 and overlaps itself. The Width of band25 is made suflicient so that the band is contained within grooves 27 ofmember 16.

Band 25 is made of a material such as cold-rolled steel which issufl'iciently flexible to permit flexing as member 16 is broken and thesegments thereof are expanded radially outward. During the expansion, anexpander cone 17 intrudes into the conically tapered lower portion ofthe inner wall of member 16 thereby breaking the member alongthelongitudinal weakened sections defined by exterior longitudinal notches22. The action of band 25 after breaking has taken place is to exertsufiicient longitudinal retaining force to prevent any broken section ofmember 16 from moving longitudinally relative to the remaining part orparts of member 16. Thus all portions of the member 16 are maintained inhorizontal alignment While being fragmented. The action of band 25 inretaining member 16 as an integral member during fracturing alsoprevents any downward movement out of contact with setting tool 14 ofthe entire integral member 16. This follows because the portion ofmember 16 which is not yet fractured still has the same inner radius ofcurvature as the portion of expander cone 12 which it is engaging. Inorder for the entire integral member 16 to slide down the expander cone12 this radius of curvature must increase. This only occurs when allbreaks along weakened sections defined by notches 22 have occurred. Thusthe entire member 16 is held in engagement with setting tool 14throughout fracturing.

Band 25, however, because of friction and composition, is a forcecompensating expansible band and, as such, does not exert an outward orinward radial spring force relative to any broken section of member 16.Any substantial radial spring action present in band 25 is counteractedby the forces of sliding friction of band 25 in recess 26a and grooves27. Thus there is no effective radial spring force applied to the brokensections by band 25.

After fracturing has occurred along the weakened sections defined bynotches 22, band 25 serves to maintain horizontal alignment of thebroken sections of member 16 as the broken sections are expandedradially outward by expander cone 17. During this movement, of course,the diameter of the assembly formed by the broken sections and linked byband 25 is steadily increasing and the overlapping portion of band 25 inrecess 2611 gets progressively shorter.

Since horizontal alignment of teeth 16a of the fractured sections ismaintained throughout the expansion of the broken sections by band 25,the teeth 16a effectively engage the wall of casing 11 in uniformhorizontal alignment and are thus enabled to bite evenly into the wallof the casing. This provides a more uniform load-distributed grip byteeth 16a than would otherwise be afforded. The overall length of band25 is desirably related to the circumference of the well casing tomaintain the interconnection of the slip segments when they are in afully expanded condition.

If a pressure differential exists across tool 12, such that the pressureis greater from above, then lower slips 20 will carry most of the load.In a case such as this, the present invention will not lose its grip oncasing 11 even if relieved of radial expansive pressure. The frictionalengagement of force compensating expansible band 25 with flanges 26 ofrecess 26a and the wall of the recess is such that the expanded slipscannot collapse radially inward. If a net inward radial pressure isapplied at only one section of the slip, as would generally be the caseif lower slip 20 were carrying most of the load, band 25 because of itsflexibility would assume an elliptical or irregular shape in grooves 27and wedge portions of its length between flanges 26 and the wall ofrecess 26a so forcefully that it will effectively lock all the brokensections into place. and prevents the loss of grip of the slips oncethey have set.

The upper surfaces 29 of the slip assembly tangs 24 are conicallytapered and engage conically tapered surfaces 30' on the lower end ofsetting tool notches 33. Similarly, the surfaces of notches 23 areconically tapered and engage conically tapered surfaces 30 on the lowerend of setting tool extensions 31. These tapered surfaces are providedto assure proper coaxial alignment of setting tool 14 and slip member 16since, as should be noted,

the inner diameter of setting tool 14 is greater than the inner diameterof the unbroken slip member 16 which is sized for a sliding fit on theouter diameter of mandrel 15. Setting tool 14, being coupled only at itsupper end to mandrel 15, could, in the absence of tapered surfaces 29and 30, be forced out of proper coaxial alignment by any component offorce transverse to its longitudinal axis which might develop during thesetting process. The provision of cooperatively engageable taperedsurfaces 29 and 30 prevents this by counteracting any such transverseforces which may develop, and thus assures proper coaxial alignment ofsetting tool 14 and slip member 16 at all times during setting andrunning-in of the well tool. The taper of the setting tool is arrangedto provide, during setting, an outward expanding force on the upper endof the slip assembly.

As upper expander cone 17 intrudes into slip assembly 16 and fracturesthe slip member into longitudinal sections, it forces the pieces of memer 16 against cooperatively aligned surfaces in the lower end of settingtool 14. Setting tool 14 is designed with notches 33 adapted to receiveraised tangs 24 of the upper end of member 16, and extensions 31 adaptedto fit into notches 23 on the upper end of assembly 16. Theconfiguration is such that each tang 24, engaging a notch 33, containstwo of the longitudinal weakening notches 22.

As more clearly seen in FIGURE 5, the result of this configuration, uponexpansion and fracture of assembly 16, is for the notches 33 in thesetting tool to each retain three of the broken sections of slipassembly 16 in each notch. This result will occur no matter in whatsequence the breaks take place along the weakened sections defined byslip notches 22. Since the tool notches 33 are symmetrically disposedabout the circumference of setting tool 14, this assures a symmetriccircumferential distribution of the broken slip segments about the innerwall of casing 11.

Although the present invention does not depend on a programmed sequenceof breaks occurring along its weakened sections defined by notches 22 asjust discussed, it should be noted that notches 22 do provide aprogrammed breaking sequence. This occurs because the weakened sectionsdefined by notches 22 which extend through the portion of slip member 16containing tangs 24 actually are stronger than the other weakenedsections because these notches are longer in a longitudinal direction.Thus the slip member will tend to break first along weakened sectionsdefined by notches 22 which extend longitudinally into slip cut outs 25.This further assists in promoting the symmetrical distribution of thebroken segments during setting. Circumferential guidance of the brokensections throughout the setting process is assured because the thicknessof annular slip member 16 and setting tool 14 is such that constantcontact between the setting tool and the slip assembly is retainedthroughout the expansion of slip assembly 16 and its engagement withcasing 11.

Thus a symmetric distribution of the broken slip elements is assured bythe present invention through the use of means retaining the brokensections in both horizontal and circumferential alignment throughout theexpansion of the slip assembly.

While the slip has been shown with a setting tool sleeve, it will bereadily apparent that a sleeve on the bridge plug operated by a settingtool will perform the same functions.

While one particular embodiment of the present invention has been shownand described, it is apparent that changes may be made without departingfrom this invention in its broader aspects and, therefore, the aim andthe appended claims is to cover all such changes and modifications asfall within the true spirit and scope of this invention.

7 What is claimed is:

1. Anchoring means for anchoring a well tool in a well bore comprising:

an annular, breakable slip assembly having spaced weakened sectionsalong its circumference adapted to break during setting of said slipassembly to form slip segments which can move radially to engage thewall of a well bore;

means for maintaining broken slip segments, when produced, in horizontalalignment;

means for maintaining a radial distribution of slip segments, whenformed, including projections on said slip member which include morethan one of said weakened sections; and

means for maintaining symmetric circumferential distribution of thebroken segments of said slip member as they move radially outward.

2. The apparatus of claim 1 wherein said weakened sections for breakingof said slip member are disposed along predetermined longitudinaldirections and are defined by longitudinal notches extending partiallythrough the thickness of said annular member.

3. An anchor system for anchoring a well tool in a well bore comprising:

at least one annular, breakable slip member;

means for breaking said slip member into longitudinal segments forsetting;

a force compensating, one-Way expansible band around an outer surface ofsaid slip member;

means for frictionally coupling said expansible band to said slipmember, said band maintaining horizontal alignment of slip segmentsproducing during setting of said slip member; and

guiding means including a sleeve member cooperatively engageable withsaid slip member for assuring a symmetric circumferential distributionof said slip segments during setting of said segments. I

4. The combination of claim 3, wherein said sleeve member has notches onthe lower end thereof adapted to receive cooperatively shaped tangs onthe upper portion of said slip member.

5. The combination of claim 3 wherein said frictional coupling meanscomprises a circumferential flanged recess in the outer surface of saidslip member.

6. An anchor system for anchoring a well tool in a well bore comprising:

an annular, one-piece, breakable slip member having circumferentiallyspaced, longitudinal weakened sections adapted to break during settingof said slip member to form longitudinal slip segments which can moveradially outward;

a force compensating, one-way expansible band about an outer surface ofsaid slip member;

a circumferentially extending grooved recess in the outer surface ofsaid slip member for retaining said expansible band on said slip member,said band maintaining broken longitudinal sections of said slip memberin horizontal alignment when said slip member is broken; and

a setting tool, including guiding notches on its lower end adapted toreceive cooperatively shaped tangs on the upper end of said slip member,said tangs and notches functioning to assure a symmetricalcircumferential distribution of said broken longitudinal segments duringsetting of said segments.

7. The apparatus of claim 6 wherein each guiding notch on said settingtool engages a tang on said slip member extending over a circumferentialportion of said slip member which includes at least two of saidlongitudinal weakened sections of said slip member.

8. The apparatus of claim 6 wherein said force compensating, one-wayexpansible band has a length such that it overlaps its end and providesa continuous horizontal support when the broken longitudinal sections ofsaid slip member move radially outward.

9. A well tool for use in a well bore comprising:

a central mandrel;

expansible packing means on said mandrel adapted to provide a seal withrespect to the wall of a well bore;

an expander cone slidably mounted on said mandrel for expanding slipanchor means radially outward into setting-engagement with the wall of awell bore;

a setting tool releasably coupled to said well tool;

slip means for anchoring said tool in a well bore including a one-piece,annular, breakable slip member having a plurality of weakened sectionsarcuately spaced about its circumference to promote breaking thereofalong predetermined longitudinal directions;

a plurality of circumferential teeth distributed along the outer surfaceof said slip member;

a force compensating, one-way expansible band around an outer surface ofsaid slip member;

a circumferentially extending grooved recess in the outer surface ofsaid slip member for retaining said expansible band on said surface,said band maintaining broken longitudinal sections of said slip memberin horizontal alignment when said slip member is broken and expandedradially outward; and

raised extensions on the upper end of said slip member said extensionscooperatively engaging guiding notches in the lower end of said settingtool and functioning to assure a symmetrical circumferentialdistribution of broken longitudinal sections of said slip member duringsetting.

10. The apparatus of claim 9 wherein each of said guiding notches in thelower end of said setting tool engages a raised extension on the upperend of said slip member which extends over a circumferential portion ofsaid slip member possessing at least two of said plurality of arcuatelyspaced weakened sections, and wherein there is at least one sucharcuately spaced weakened section provided in said slip member betweeneach pair of said raised extensions.

References Cited UNITED STATES PATENTS 2,966,216 12/1960 Bigelow 1661343,062,295 1 1/ 1962 Hanes 2771l6.2 3,229,767 1/1966 Carter 1661343,285,343 11/1966 Urbanosky 166135 X 3,344,861 10/1967 Claycomb 166134 X3,412,803 11/1968 Stachowiak 166134 DAVID H. BROWN, Primary Examiner US.Cl. X.R.

22 U93 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3 Dated February 97 lnventofls) William O. Berryman It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 41 (application Page 2, line 15) "dring" should readduring Column 5 line 65 (application Page 12, line 9) add the following:

mm m RPMFU $EP15197U lqn (SEAL) Am Edna ll- Fletch, I. :0 W, m- MugOfficer III-Iliumof Patents Band 25 behaves, therefore, as a one-wayexpansible band 'ORM PO-IOEO H049) UsCOMM-pg; 50375-959 ILL GOVIINIIIIITPIIITIIG OFFICI "II O-lU-Sl

